explains about dart classes - methods, final,static and basic inheritance

classes.dart

void main() {
  var n1 = Complex(3, -2);
  var n2 = Complex(1, 4);

  print(n1 + n2);
  print(n1.multiply(n2));
  print(Complex.substract(n1, n2));
  print(Complex.counter);
  print(Quaternion(1,-2,-3));
}
//   var c = Complex(3, 8);

//   var c2 = Complex(9, 2);
//   var r = Complex.real(10);
//   var i = Complex.imaginary(3);
//   i.imaginary = 20;
//   i.real = 334;

//   i.real;
//   i.imaginary;

//   print(c == c2);

//   print(c);
//   print(c2);
//   print(r);
//   print(i);

class Complex {
  num _real;
  num _imaginary;

  static num counter = 0;

  get real => _real;
  set real(num value) => _real = value;

  get imaginary => _imaginary;
  set imaginary(num value) => _imaginary = value;

//   num getReal(){
//     return _real;
//   }

//   void setReal(num real){
//     this._real = real;
//   }

//   num getImaginary(){
//     return _imaginary;
//   }

//   void setImaginary(num imaginary){
//     this._imaginary = imaginary;
//   }

  Complex(this._real, this._imaginary) {
    counter = counter + 1;
  }

  Complex.real(num real) : this(real, 0);
  Complex.imaginary(num imaginary) : this(0, imaginary);

  Complex multiply(Complex c) {
    var first = this.real * c.real;
    var inner = this.imaginary * c.real;
    var outer = this.real * c.imaginary;
    var last = -(this.imaginary * c.imaginary);
    return Complex(first + last, inner + outer);
  }

  Complex operator +(Complex c) {
    return Complex(
      this.real + c.real,
      this.imaginary + c.imaginary,
    );
  }

  static Complex substract(Complex c1, Complex c2) {
    return Complex(c1.real - c2.real, c1.imaginary - c2.imaginary);
  }

  @override
  bool operator ==(other) {
    if (!(other is Complex)) {
      return false;
    }
    return this._real == other.real && this._imaginary == other.imaginary;
  }

  @override
  String toString() {
    if (_imaginary >= 0) {
      return "$_real + ${_imaginary}i";
    }
    return "$_real -  ${_imaginary.abs()}i";
  }
}

class Quaternion extends Complex {
  num jImage;

  Quaternion(
    num real,
    num imaginary,
    this.jImage,
  ) : super(
          real,
          imaginary,
        );

  @override
  String toString() {
    if (this.jImage >= 0 && this._imaginary >= 0) {
      return '${this._real} + ${this._imaginary}i + ${this.jImage}j ';
    }
    if (this.jImage >= 0 && this._imaginary < 0) {
      return '${this._real} - ${this._imaginary.abs()}i + ${this.jImage}j ';
    }
    return '${this._real} - ${this._imaginary.abs()}i - ${this.jImage.abs()}j ';
  }
}